U.S. Pat. No. 6,935,595 and US 2009/0015436 disclose a guidance apparatus mounted on the belly of a tanker aircraft that provide visual indications to the receptor pilot to facilitate the approaching operation for carrying out a refueling operation using a refueling boom which is based on light emitting devices, called Pilot Director Lights (PDLs), comprising one or more light emitting diodes (LEDs) modules and control devices for controlling the current supplied to each LEDs module.
Said guidance apparatus includes a dimming capability for regulating the level of the light intensity of the LEDs modules that has the following drawbacks:                The light intensity is too high for receiver pilots in night ambient conditions. This amount of light is annoying and affects the workload of receiver pilots during a refueling operation.        When the dimming control slightly decreases below the minimum level, the LEDs modules are unexpectedly switched off. Sometimes a light flashing is noted resulting in a very annoying situation for a receiver pilot, who is blinded with this intermittent effect.        